- conn.go: Write() now writes first then records b[:n] (not len(b)),
matching the Read() pattern and preventing phantom data on failures.
- handler.go: add nil Router check before h.options.Router.Dial()
in Handle's non-hop path to return a clear error instead of panicking.
- handler.go: guard h.options.Router against nil in forwardSerial;
restructure if/else so ReadTimeout is applied in both the direct
OpenPort path and when the Router has no chain configured.
ginuerzh